Fuel cells, in particular PEFCs or PEMFCs (hereinafter just PEMFCs), have been considered for power generation applications for many years. Many innovative improvements in operational performance capability have been achieved. Specifically, efficiencies have been increased to 65% at 1 amp/cm.sup.2 ; water/thermal management problems have been resolved; and the use of thin film polymer electrolyte (or proton exchange membranes) with reduction in the thin film catalyst layers has been achieved. Additionally, increased energy density, both gravimetric at 60 Watts/lb, and volumetric at 5000 Watts/ft.sup.3, with stack sizes of approximately 1.5 to 20 KW are now available.
The potential use of PEMFCs as commercially viable alternatives to high energy density batteries, or different types of fuel cells such as PAFC, MCFC, and SOFC, is limited primarily by manufacturing cost considerations, and has consequently limited the general acceptance of PEMFCs in many applications. PEMFCs offer comparable performance as the other fuel cell candidates, at significantly lower operating temperatures, and potentially lower maintenance. Life expectancy/reliability, vs the high energy density battery candidates is significantly better, as compared to the total number of recharge cycles that can be achieved. These factors indicate that PEMFC market potential, for applications in mobile land-based vehicles, submersible manned vehicles, AUV work vehicles, and fixed-site utility power generation, etc., is primarily limited by a cost threshold not realized by existing configuration.
This threshold, at approximately $1000/KW, (1993 dollars) would enable PEMFCs to be considered for utility power applications, and, with their approximately 25% improvement over competitive coal-fired power plant throughput efficiency, could be an economically viable choice, providing reduced fuel consumption costs. Similarly, for mobile applications, wherein gravimetric and volumetric energy density is also of critical importance, performance vs cost tradeoffs dictate whether they offer an economically viable choice vs the alternative battery candidates.
These varied applications run the gamut from required power output capability from 1.5 to greater than 2 MW. Any specific design embodiment for a unique application implies a limited market niche, and consequently an inability to realize the economies of scale to be realized in high volume manufacturing operations. These design specific embodiments may possess relatively high efficiency, but at a penalty of reduced energy density. Similarly, they may possess low efficiency but at a high energy density. Additionally, they may be more readily suited to operation using stored fuel and oxidant supplies, vs using reformed fuel and air.
In summary, the selection of PEMFCs over the alternative candidate solutions for power generation would be enhanced, if the preferred embodiment of the design provided a modular/building block stack assembly providing high efficiency, high energy density, amenable to low cost of manufacturing, and capable of providing output power generation in 7.5, 15, 30, 60, 240 KW (and higher) increments, such that tailoring to the application intended is facilitated. This basic building block stack or module, would provide a single solution for the variety of applications, and realize additional economies of scale through a larger market potential capability.